Windshield cleaning system for motor vehicles

ABSTRACT

A WINDSHIELD WIPER CONTROL SYSTEM FOR PRODUCING TIMED DWELL PERIODS BETWEEN EACH CYCLE OF WINDSHIELD WIPER OPERATION IS PROVIDED WITH A MANUALLY SETTABLE TIMING NETWORK INCLUDING A TRANSISTOR WHICH CONTROLS THE ENERGIZATION OF A CIRCUIT INTERRUPTER. THE CIRCUIT INTERRUPTER IS CONNECTED IN PARALLEL WITH A CYCLICALLY ACTUATED, MOTOR OPERATED PARKING SWITCH. THE PARKING SWITCH OPENS TO STOP THE WIPER MOTOR AT THE END OF EACH CYCLE. IN A PRESET TIME INTERVAL AFTER STOPPING, THE TIMING NETWORK OPERATES TO ACTUATE THE CIRCUIT INTERRUPTER THUS RESTARTING THE MOTOR. THE MOTOR REMAINS ENERGIZED THROUGH THE PARKING SWITCH UNTIL THE NEXT DWELL PERIOD. THE TIMING NETWORK INCLUDES A MANUALLY VARIABLE RESISTOR WHICH CONTROLS THE DISCHARGE TIME OF A CAPACITOR. THE TRANSISTOR IS TRIGGERED CONDUCTIVE WHEN THE CAPACITOR IS CHARGED. THE TIMING NETWORK IS ENERGIZED BY A SWITCH RESPONSIVE TO MOTOR ROTATION.

July 4, 1972 w. c. RIESTER Re. 27,423

WINDSHIELD CLEANING SYSTEM FOR MOTOR VEHICLES Original Filed Dec. 16,1963 2 Sheets $heati1 INVENTOR WILLIAM c. R/ESTER avg wa A TTORNEY w. c.RIESTER Re. 27,423

WINDSHIELD CLEANING SYSTEM FOR MOTOR VEHICLES July 4, 1972 2 sheetssheetj Original Filed Dec. 16, 1963 INVENTOR. WILL/AM C- R/ESTERATTORNEY United States Patcnt Oflice Re. 27,423 Reissued July 4, 1972Int. Cl. 1360s 1/08 U.S. Cl. 318-443 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A windshield wiper control system forproducing timed dwell periods between each cycle of windshield wiperoperation is provided with a manually settable timing network includinga transistor which controls the energization of a circuit interrupter.The circuit interrupter is connected in parallel with a cyclicallyactuated, motor operated parking switch. The parking switch opens tostop the wiper motor at the end of each cycle. In a preset time intervalafter stopping, the timing network operates to actuate the circuitinterrupter thus restarting the motor. The motor remains energizedthrough the parking switch until the next dwell period. The timingnetwork includes a manually variable resistor which controls thedischarge time of a capacitor. The transistor is triggered conductivewhen the capacitor is charged. The timing network is energized by aswitch responsive to motor rotation.

The present invention relates to a control system for motors and, moreparticularly, to a control system for windshield wiper motors whichprovide a dwell period between cycles of wiper operation.

Under certain road travel conditions such as in light or moderate rain,and on roads wet with the residue of rain where wheel spray from passingvehicles tends to partially obstruct vision, continuous wiper operationmay cause smearing of wet film deposits created by the continuouslymoving blade. Furthermore, excessive wear of the wiper element resultsbecause of inadequate wetting of the windshield, necessary for properlubrication. Another objectionable feature of conventional continuouslyoperated windshield wipers is the driver fatigue induced by the constantback and forth movement of the wiper.

Intermittent dwell wiper systems wherein a dwell period is providedbetween cycles of wiper operation overcome the above-mentioneddisadvantages of the present continuous wiper motion. During the dwellperiod the windstream against the windshield created by vehicle motionis used advantageously to dry and dissipate the thin film of visionobscuring moisture which is created by wiper operation on a wet-drywindshield. The dwell period providcs discontinuity in wiper motion,avoiding monotony generated driver fatigue and frequency of wiperoperation is reduced thereby prolonging blade life. The reduction inwiper frequency is accomplished while maintaining optimum wiper velocityas the wiper traverses its wiping path. With multispced and variablespeed continuous run wipers, change in wiper speed from the optimumspeed can produce blade chattering and imperfect wiping.

Reliable intermittent dwell wiper systems have been developed whichprovide all of the advantages above mentioned. Such systems areillustrated in U.S. Patent No. 2,987,747 by J. R. Oishei ct al., issuedJune 13, 1961,

U.S. Patent No. 3,110,056 by J. R. Oishei et al., issued Nov. 12, 1963,and in U.S. Patent No. 3,117,335 by I. R. Oishei et al., issued Jan. 14,1964.

The principal object of the present invention is to provide an improvedcontrol system for producing intermittent dwell windshicld wiperoperation utilizing a minimum number of control elements.

Another object of the invention is to provide an improved control systemfor producing intermittent dwell windshield wiper operation wherein theduration of the dwell period is controllable and consistent for anyselected period within the operating range of the system.

A further object of the invention is to provide an improved controlsystem for producing intermittent dwell windshield wiper operation whichprovides for continuous wiper operation as well as controllable dwellperiods correlated to the wiper oscillation with the time base of thedwell period being reset during every wiping cycle.

A still further and more specific object of the inven tion is to providean improved intermittent dwell windshield wiper system for a motorvehicle utilizing a minimum number of elements including stable, staticdevices, wherein the duration of the dwell period is controllable toprovide continuous wiper operation or intermittent dwell wiper operationwith consistent, selected dwell periods and which provides continuouswiper operation for a. controlled period automatically in response tovehicle acceleration.

Although the invention is particularly useful in connection with a motorvehicle windshield wiper system and is shown and described in such asystem, it will of course be understood that the control system of thisinvention in accordance with the broader aspects thereof can be employedin any system where controllable intermittent motor output is desirable.

Other objects and advantages of the invention will be apparent from thefollowing detailed description taken in connection with the accompanyingdrawings in which:

FIG. 1 is a partial perspective view of a motor vehicle embodying theinstant invention;

FIG. 2 is a perspective view illustrating the contacts of the controlsystem which are positioned with the gear reduction unit housing;

FIG. 3 is a partial elevational view of the gear reduction unit with thecover removed;

FIG. 4 is a longitudinal sectional view of the vacuum operated switch;

FIG. 5 is a front elevational view of the manual control and dial; and

FIG. 6 is a schematic diagram showing the electrical system of thecontrol system.

Briefly, the invention comprises a control system for a motor whichdrives a pair of windshield wiper blades through a gear reductionarrangement and a linkage system. The control system includes a relayhaving its contacts connected in parallel with the contacts of theparking switch in the supply line for the motor. The parking switch isinternal and opens only when the motor is in such a position as to placethe wiper blades in parked position. The relay is normally closed andactuated to open position by a timing network. The basic elements of thetiming network comprise a pnp transistor connected in parallel with aselectively variable resistor which may be manually operated and acapacitor connected across a DC power supply through a normally opencharging switch. The charging switch has its contacts positioned withinthe housing of the gear reduction unit and is actuated to closedposition by a cam on the output gear of the gear reduction unit, whichcam operates the charging switch and the. parking switch sequentiallyonce during each revolution. Closing of the charging switch effectscharging of the capacitor and biases the base of the transistor negativewith respect to the emitter. The momentar y closing of the chargingswitch resets the time base of the dwell period to correlate the timeperiod with the wiper oscillation. As the cam leaves the movablecontactor of the charging switch, effecting opening thereof, thecapacitor discharges through the variable resistor. Biasing the basenegative with respect to the emitter causes current to flow in theemitter-collector circuit. The coil of the relay is connected in seriesin the emitter-collector circuit and is energized by current flowthrough this circuit. Energization of the coil effects opening ofcontacts in the supply line to the motor. However, the supply lineremains closed by the parallel connected parking switch until the cam onthe output gear of the gear reduction unit causes opening of the parkingswitch when the wiper blades are in the parked position. The duration oftime during which the capacitor discharges is regulated by the value ofthe resistance in the variable resistor. Increase in the resistanceincreases the duration of time during which the capacitor isdischarging. When the capacitor is discharged to a value insufficient tomaintain the proper negative bias on the transistor base,emitter-collector current ceases, the relay contacts reclose, and themotor is restarted. This same cycle repeats itself when the motor againdrives the cam on the output gear to cause closing of the chargingswitch. Setting the variable resistance to a very small or zero valueresults in rapid discharge of the capacitor causing closing of the relaycontacts prior to opening of the parking switch, thereby resulting incontinuous wiper operation.

To automatically effect continuous wiper operation during acceleration,a vacuum responsive switch having its contacts connected across thevariable resistor is provided and may be responsive to manifold vacuum.During acceleration when the vacuum in the manifold line falls to a verylow value, the contacts in the vacuum control switch close, shorting outthe variable resistor thereby resulting in continuous wiper operation.

In FIG. 1 an automotive vehicle is shown having a windshield 12 mountedthereon in a conventional manner. A windshield power unit 15 (indicatedschematically in FIG. 6) including a wiper motor 14 and a gear reductionunit 16 is mounted on the fire wall 18 of the vehicle. The gearreduction unit has a crankarm 20 operatively coupled thereto. Anelongated link 22 is pivotally secured to the crankarm 20 through asecond elongated link 24. Opposite ends of the link 22 are connected tocrankarms 26 mounted at the inner ends of rockshafts or pivot shafts(not shown), which pivot shafts are journaled in the cowl of the vehicleand have wiper arms 28 mounted at their outer ends. The wiper arms eachcarry wipers 30. When the wiper motor 14 is energized. the wipers 30will be oscillated across the windshield to clear moisture therefrom.The gear reducer unit 16, crankarms 20 and 26, links 22 and 24 and therockshafts constitute the wiper transmission means.

A control housing 32 containing the components indicated by broken linesin FIG. 6 is mounted on the inner side of the dash panel of the vehicle.A stem for controlling the movable contact of the variable resistor 34projects outwardly toward the passenger compartment and has a knob 36 atthe free end thereof. An indicating pointer 38 is provided which ismovable with the stem and knob 36. A dial 40 graduated in dwell durationintervals is provided concentric with the stem on the outer side of thedash panel. A harness 42 of electrical conduit extends outwardly fromthe control housing 32 connecting the control system to the wiper powerunit 15 and to the vacuum operated switch 44. A conduit 46 conmeets thevacuum operated switch 44 to the intake manifold 48 on the vehicleengine. The vacuum operated switch 44 may be mounted in any suitablelocation as, for example, on the fire wall 18 of the vehicle. Thevehicle 10 is provided with a battery 50 which serves as a power supply.The negative terminal of the battery 50 may be grounded to a commonground system.

The motor 14 of the power unit 15 is connected across the power supply50 through conductor 52, junction 54, conductor 56, junction 58,conductor 60, brushes 62 in parallel with field winding 64 throughjunction 66 and normally closed parking switch 68 to ground. Fromjunction 66 the motor is alternatively connected to ground or negativeside of the power supply through lead 70, stationary contact 72 of relay74, movable contact 76 of relay 74, lead 80 and manual on-ofl switch 82to the ground or negative terminal of the power supply. Thus it can beseen that the motor may be deenergized by opening manual switch 82 or byopening of the normally closed relay contacts 72, 76 when the camactuated parking switch is opened.

The relay contacts 72, 76 of relay 74 are actuated to open position uponenergization of coil 73 of relay 74. Coil 73 is energized through thetiming network 84. The timing network 84 comprises a pnp transistor 86having a collector 88, an emitter 90 and a base 92. The timing network84 further includes the manually operated variable resistor 34 and acapacitor 94. The emitter-base circuit of the transistor 86, thecapacitor 94 and the variable resistor are connected in parallel acrossthe power supply through a current limiting resistor 96 and the chargingswitch 98. Connected in series with the base of the transistor 90 is acurrent limiting resistor 100 for protecting against over-currentthrough the transistor.

The capacitor is connected across the power supply 50 through lead 52,junction 54, current limiting resistor 96, lead 102, capacitor 94, lead104, junction 106, lead 108, charging switch 98 to ground. The manualvariable resistor 34 is connected across the power supply throughpostive lead 52, junction 54, current limiting resistor 96, movablecontactor 110, resistance 34, junction 106, lead 108 and charging switch98 to ground. The emitter-base circuit of the transistor 90 is connectedacross the power supply through positive lead 52, resistor 96, lead 102,emitter 90, resistor 100, lead 112, junction 106, lead 108 and chargingswitch 98 to ground. The emitter-collector circuit of the transistor isconnected across the power supply from positive lead 52, currentlimiting resistor 96, lead 102, emitter 90, collector 88, lead 114, coil73 of relay 74 and switch 82 to the negative side of the power supply orground. The vacuum operated switch 44 having contactor 118 comprisingmovable contact 1180. and stationary contact 118b is connected acrossthe resistor 34 from junction 120 through lead 122, contactor 118 andlead 124 to junction 126. It will thus be apparent that when thecontactor 118 is closed, the resistance 34 is lay-passed. The parkingswitch 68 and the charging switch 98 in the above described circuitryare operated by a cam on the output gear of the gear reduction unit 16.

The gear reduction unit 16 includes a housing secured to the motor framewith the shaft 132 of the motor extending through the housing. The shaft132 has formed thereon a spur gear 134 which meshes with idler gear 136.The idler gear 136 has mounted for rotation and concentric therewith apinion 138 which meshes with the output gear 140 of the gear reductionunit. The unit gear 140 has formed thereon a cam 142. Secured to thehousing 130 is a contactor assembly 144 including a terminal block 146having terminals 148, 150 and 152 thereon. Terminal 152 is connected toground through stationary contact 154 and movable contactor 156 whichform the charging switch 98. Terminal 150 is connected to ground throughstationary contact 158 and movable contactor 160 which form the parkingswitch 6-8. The movable contactors are positioned on a common are andare engaged sequentially by the cam 142 as the output gear 140 isrotated counterclockwise thereby closing charging switch 98 andsubsequently opening parking switch 68 after opening of charging switch98.

The vacuum control switch 44 comprises a housing 162 having a base 164of insulating material and a cover 166 which may be secured to the baseor crimped thereto in any suitable manner. Movable contactor 118a issecured to the insulating base in any suitable manner as, for example,by a connecting rivet 168 as shown. Stationary contact 11% is secured tothe base 164 in any suitable manner for engagement with movablecontactor 118a. The conducting rivet 168 extends through the base 164and has secured at its outer end a terminal 170 to which is secured lead124. The stationary contact 118b extends through the base 164 to theouter side thereof and has secured at its outer end a terminal 172 towhich is secured lead 122. The housing cover 166 and the base 164 form aclosed chamber 173 divided by a diaphragm 174 having its peripheraledges interposed between annular flanges on the cover 166 and the base164. The diaphragm divides the chamber 173 into a compartment 173a and acompartment 173b. A spring 176 is disposed in compartment 173a andextends between the upper surface of the cover 166 and a retaining plate181} lying in juxtaposition with the diaphragm 174. A nipple 182 havinga conduit therethrough leading to the compartment 173a is formed on thecover 166 and hose conduit 46 is secured thereto. Vacuum from the intakemanifold 48 is admitted through hose 46 and nipple 182 to compartment173a. The diaphragm is moved upwardly from a position seen in FIG. 4against the bias of the spring 176 to permit normally closed contactor118 to open. During the acceleration of the vehicle when the vacuumpressure of the intake manifold 48 drops and the pressure in the chamber173 equalizes on opposite sides of the diaphragm, the spring 176 causesthe diaphragm to move to the position seen in FIG. 4 thereby closingcontactor 118.

The operation of the control system should now be apparent. When theknob 3-6 on the dash panel is turned to the continuous positionindicated by C in FIG. 5 on the dial 40, the switch 82 is closed and thecontactor 110 of the variable resistor 34 is at its end position A,thereby bypassing the resistor 34. The motor is then energized andcauses rotation of the output gear 140 in counterclockwise direction asseen in FIG. 3. Continued rotation of the knob 36 introduces increasingsegments of resistance 34, thereby increasing the duration of the dwellperiod. When the cam 142 engages the movable contactor 156 on thecharging switch 98 the switch closes, placing the capacitor 94, theselected segment of resistance 34 and the emitterbase circuit of thetransistor 86 across the power input. This causes the capacitor tobecome charged as indicated in FIG. 6 and biases the base negative withrespect to the emitter. When the cam 142 leaves the contactor 156, theswitch opens and the capacitor 94 discharges through the selectedsegment of resistance 34. The rate at which the capacitor dischargesdecreases with increasing resistance 34 so that continued clockwiserotation of knob 36 introduces more resistance and decreases thedischarge rate of capacitor 94. As the discharge rate decreases, thebase of the transistor 86 remains biased negative for a greater durationof time. When the base of the transistor is biased negative with respectto the emitter, the emittercollector conducts thereby energizing coil 73of relay 74, effecting opening of contactor 76. Contactor 76 remainsopen so long as the transistor emitter-collector circuit is conducting.When the cam 142 in continuing its clockwise rotation engages contactor160, the parking switch 68 opens. Thus with contactor 76 and switch 68opened, the input to the motor is interrupted and the motor stops. Whenthe capacitor 94 has completed its discharge or has become discharged tosuch a low value of voltage as to effectively decrease the negativ biason the base of the transistor to cut off, the collector emitter circuitceases to conduct and the contactor 76 closes, thereby restarting themotor.

If the vehicle is accelerated, the vacuum pressure in the intakemanifold 48 drops causing spring 176 to bias diaphragm 174 downwardlyclosing contactor 118. Closing of contactor 118 results in bypassing ofthe resistor 34 and is tantamount to maintaining the pointer 38 at theposition C of the dial. In other words, the resistor 34 is effectivelyremoved from the timing network. Removal of the resistance 34 from thetiming network permits the capacitor 94 to discharge so rapidly that theemitter-collector circuit of the transistor 86 ceases conduction beforethe parking switch 68 is opened by the cam 142; thus continuousoperation results.

Since the load on the elements of the timing circuit is so small, theelectrical characteristics do not vary through the range of theresistance 34 and the timing cycle remains precisely consistent.Furthermore, a consistent dwell period is assured during every cycle ofwiper 0pera tion because the momentary closing of charging switch 98effects resetting of the time base. Thus at a given setting of thepointer 38 on the dial 40, there will be substantially no variation inthe duration of dwell and, further, since the elements are lightlyloaded and are inherently stable, there is no substantial wear on thetiming circuit and long life of the control system can be expected.Although the relay 74 includes a moving contactor 76, the contactor 76never opens a circuit, but only closes a circuit. Thus there can be nodestructive arcing at the contacts and long and consistent life can beexpected from this component.

It should now be apparent that a unique control system for intermittentdwell operation of a motor has been provided which is particularlysuitable for intermittent dwell windshield wiper operation. A specificembodiment of the invention has been described for the purpose ofillustration, but it will be apparent that various modifications andother embodiments are possible within the scope of the invention. Forexample, in accordance with the broader aspects of the invention, otherand diiferent physical constructions of the parking and chargingswitches may be employed, as well as other and different constructionsof the vacuum operated switch. In accordance again with the broaderaspects of the invention, a manually operated switch or a switchresponsive to other and different conditions may be substituted for thevacuum operated switch. The variable resistor 34 may be selectivelyvariable by means other than manual operation. Further, by employingcertain obvious circuit modifications an npn transistor or otherresponsive bi-stable switching devices may be employed. The motor may beemployed for other and different purposes. It is to be understood,therefore, that the invention is not limited to the specific arrangementshown, but in its broadest aspects it includes all equivalentembodiments and modifications which come with the scope of theinvention.

What is claimed is:

I. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network including input means and output means, a normally closedcircuit interrupter opened when energized, actuated by said output meansand having contacts connected in circuit with said motor, means forapplying energy pulses to said input means, said timing networkincluding means for converting energy pulses applied to said input meansto output energy pulses of a controlled duration independent of theduration of the energy pulses applied to the input means and means forapplying said output pulses to said circuit interrupter whereby saidcircuit interrupter is energized to effect openin of the motor circuit.

2. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network, means for momentarily applying an in- 7 put to saidtiming network in response to motor rotation and means for convertingsaid momentary input to an output of controlled duration and frequency,a normally closed circuit interrupter actuated to open position whenenergized having contacts in circuit with said motor, and means forenergizing said circuit interrupter from the output of said timingnetwork.

3. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network, means for momentarily applying an input to said timingnetwork in response to motor rotation and means for converting saidmomentary input to an output of controlled duration and frequency, anormally closed circuit interrupter actuated to open position whenenergized having contacts in circuit with said motor, and means forenergizing said circuit interrupter from the output of said timingnetwork, normally closed switch means for by-passing said circuitinterrupter contacts and means for opening said switch means at aselected wiper blade position.

4. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network, means for momentarily applying an input to said timinnetwork in response to motor rotation and means for converting saidmomentary input to an output of controlled duration and frequency, anormally closed circuit interrupter actuated to open position whenenergized having contacts in circuit with said motor, and means forenergizing said circuit interrupter from the output of said timingnetwork, normally closed switch means for by-passing said circuitinterrupter contacts and means for opening said switch means at aselected wiper blade position and automatic means responsive to externalconditions for reducing the duration of said timing network output pulseto a value suflicient to effect reclosing of said circuit interrupterprior to the opening of said normally closed switch means.

5. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network including an energy storing device, impedance means forlimiting the discharge rate of said energy storing device and a Staticswitching device, switch means responsive to motor rotation formomentarily energizing said energy storing device and for biasing saidstatic switching device to a conducting state, said static switchindevice being maintained in a conducting state during the discharge ofsaid energy storing device, said energy storing device being connectedin circuit with said impedance means, a normally closed circuitinterrupter, open when energized having an actuating coil in circuitwith said static switching device and being energized when said staticswitching device is in a conducting state and being deenergized whensaid static switching device is in a non-conducting state, said circuitinterrupter having contacts in circuit with said motor.

6. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving and wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network including an energy storing device, impedance means forlimiting the discharge rate of said energy storing device and a staticswitching device, switch means responsive to motor rotation formomentarily energizing said energy storing device and for biasing saidstatic switching device to a conducting state, said static switchingdevice being maintained in a conducting state during the discharge ofsaid energy storing device, said energy storing device being connectedin circuit with said impedance means, a normally closed circuitinterrupter, open when energized having an actuating coil in circuitwith said static switching device and being energized when said staticswitching device is in a conducting state and being deenergized whensaid static switching device is in a non-conducting state, said circuitinterrupter having contacts in circuit with said motor and control meansfor varying the value of said impedance to regulate the duration of thedwell period.

7. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network including an energy storing device, impedance means forlimiting the discharge rate of said energy storing device and a staticswitching device, switch means responsive to motor rotation formomentarily energizing said energy storing device and for biasing saidstatic switching device to a conductive state, said static switchingdevice being maintained in a conducting state during the discharge ofsaid energy storing device, said energy storing device being connectedin circuit with said impedance means, a normally closed circuitinterrupter, open when energized having an actuating coil in circuitwith said static switching device and being energized when said staticswitching device is in a conducting state and being deenergized whensaid static switching device is in a non-conductin state, said circuitinterrupter having contacts in circuit with said motor and means forbypassing the impedance to produce continuous wiper cycling.

8. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network including an energy storing device, impedance means forlimiting the discharge rate of said energy storing device and a staticswitching device, switch means responsive to motor rotation formomentarily energizing said energy storing device and for biasing saidstatic switching device to a conducting state, said static switchingdevice being maintained in a conducting state during the discharge ofsaid energy storing device, said energy storing device being connectedin circuit with said impedance means, a normally closed circuitinterrupter, open when energized having an actuating coil in circuitwith said static switching device and being energized when said staticswitching device is in a conducting state and being deenergized whensaid static switching device is in a nonconducting state, said circuitinterrupter having contacts in circuit with said motor and meansresponsive to vehicle acceleration for by-passing and impedance means toproduce continuous wiper operation.

9. In a windshield cleaning system for a motor vehicle including a setof windshield wipers and a motor operatively connected thereto fordriving said wipers; a control system for said motor to providecontrolled dwell periods between cycles of wiper operation comprising atiming network including an energy storing device, impedance means forlimiting the discharge rate of said energy storing device and a staticswitching device, switch means responsive to motor rotation formomentarily energizing said energy storing device and for biasing saidstatic switching device to a conducting state, said static switchingdevice being maintained in a conducting state during the discharge ofsaid energy storing device, said energy storing device being connectedin circuit with said impedance means, a normally closed circuitinterrupter, open when energized having an actuating coil in circuitwith said static switching device and being energized when said staticswitching devce is in a conducting state and being deenergized when saidstatic switchng device is in a non-conducting state, said circuitinterrupter having contacts in circuit with said motor and normallyclosed switch means by-passing said circuit interrupter contacts, saidnormally closed switch means being opened when said wipers are in parkedposition.

10. Windshield wiper control mechanism for a wiper movable back andforth across the surface of a windshield including, an electric motoroperable to oscillate the wiper and park the wiper in a predeterminedposition, an electric power source, an energizing circuit for said motorincludnig a cyclically actuated parking switch operated by said motor,interrupter means connected in parallel with said parking switch in saidenergizing circuit, variable timing means connected in circuit with saidinterrupter means, said timing means including means responsive to motorrotation for establishing a time base and for carrelating the timedperiod to the wiper oscillation by resetting said time base during everywiping cycle and a manual control connected with said power source andReferences Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 11/1965 Foreman et al. 318-443 7/1966 Amos 318-443I. D. MILLER, Primary Examiner R. J. HICKEY, Assistant Examiner US. Cl.X.R. 318DIG 2 Patent No. 271423 D t d July 4, 1972 Inventor(s) W. C.Riester It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Col. 7, line 67, change "and" to -said-; Col. 8, line 57, change "and"to -said-; Col. 9, line 2, change "switchng" to --switching----; Col. 9,line 13, change "includnig" to including-.

Signed and sealed this 13th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

Commissioner of Patents

